Universitas Scientiarum

The Avoidance Spectrum of Alexandroff Spaces

Luis Mejias — 2024-05-04

In this paper we prove that every T0 Alexandroff topological space (X, τ ) is homeomorphic to the avoidance of a subspace of (Spec(Λ), τ_Z), where Spec(Λ) denotes the prime spectrum of a semi-ring Λ induced by τ and τ_Z is the Zariski topology. We also prove that (Spec(Λ), τ_Z) is an Alexandroff space if and only if Λ satisfies the Gilmer property.

Enhancing the functional characteristics of sago starch through dual chemical modification by hydroxypropylation and succinylation

Derina Paramitasari — 2024-08-12

Sago starch is a locally abundant starch indigenous of Indonesia. Despite its abundance, it is underutilized and restricted to food and packaging applications due to its limited functional characteristics. The value of native sago starch can be increased through modifications that improve its functionality, such as dual chemical modification. This sophisticated approach is more effective than single modification and makes the starch suitable for wider applications. Our study aimed to determine if dual chemical modification involving hydroxypropylation and succinylation would optimize the functional properties of sago starch. The sago starch was first modified by hydroxypropylation with 7 % (w/w) propylene oxide under alkaline conditions for 3 hours. This process resulted in hydroxypropylated starch with a substitution degree of 0.107. We then subjected the starch to succinylation using succinic anhydride at 1 % to 5 % of the starch weight in an alkaline solution for 2 hours.We achieved optimal functional characteristics of the dual-modified sago starch in the sample modified with 3 % (w/w) of succinic anhydride. The succinyl degree of substitution, water holding capacity, oil holding capacity, swelling power, and solubility of the dual-modified starch were 0.093, 4.16 g g⁻¹ , 7.20 g g⁻¹, 34.25 g g⁻¹, and 16:55 %, respectively. We conducted pasting properties analyses, infrared spectroscopy, and morphological structure analysis to determine the changes in the characteristics of the sago starch after hydroxypropylation and succinylation. The dual chemical modification successfully enhanced the functional characteristics of sago starch, particularly, its amphiphilic ability and swelling power.

These results warrant further research and development in commercial applications.

Optimization of a novel Renealmia ligulata (Zingiberaceae) essential oil extraction method through microwave-assisted hydrodistillation

José Leonardo Cano Botero — 2024-05-21

Renealmia is a tropical plant genus within the Zingiberaceae family. In tropical South America, Renealmia plants are known for their therapeutic uses against bone and muscle pain, colds, and to counteract snake bite symptoms. Despite the biomedical importance of Renealmia metabolites, the components of their essential oils (EO) have been scarcely studied, and a cause thereof is the lack of local efficient, inexpensive, and environmentally friendly EO extraction methods. This work addressed the optimization of an EO extraction method from the aerial parts and rhizomes of Renealmia ligulata plants based on microwave-assisted hydrodistillation (MAHD) with an ultrasound-assisted extraction (UAE) pretreatment. Three MAHD extraction variables (radiation power, radiation exposure length, and solvent volume) were studied on their own and in combination using a response surface analysis to determine the value combinations leading to optimal EO yields. The results showed that the best average extraction duration time was 42.5 min, combined with a radiation power of 765 W and a solvent volume 225.9 mL for 30 g of aerial part plant material or 799 W and 145 mL of solvent for 20 g of plant rhizomes. A GC-MS analysis of the obtained R. ligulata EOs revealed that their main component was epi-Eudesmol (28% in plant aerial parts and 13% in rhizomes), which is a molecule of interest considering its reported neuro-protective properties.

Organoleptic, chemical composition, and histology of fresh vs. fried Indonesian anchovies (Stolephorus sp.)

Agoes Mardiono Jacoeb — 2024-08-23

Fried anchovy (Stolephorus sp.) is a popular food in Indonesia due to its good taste and ample availability and affordability. Yet, the actual nutritional aspects of this local dish remain uninvestigated. This study imed to determine the best temperature and time for frying anchovies and to compare the histology and fatty acid and cholesterol profiles of fresh and fried anchovy meat. Anchovies were fried at 160 °C or 180 °C for 5, 10, 15, and 20 minutes, and the best frying conditions, namely at 180°C for 15 minutes, were established from the highest organoleptic test scores from a tasting panel assessment. Histologically, fried anchovy meat became shrunk, compact, and brittle, as explained by identified myomere changes. The fatty acid profile of fresh vs. fried anchovies revealed a marked reversal in omega-6: omega-3 ratios, and fried anchovies contained more cholesterol than fresh ones (0.825 mg/100 g vs. 0.270 mg/100 g, respectively). These changes were triggered by the use of oil and the temperature-driven chemical changes inherent to the frying process. Having investigated the organoleptic and nutritional aspects of frying anchovy meat, we propose the results of this investigation as a guide for dietary decisions and as a reference for further investigation on the subject.

Development of a Bioreactor-Based Model for low-density polyethylene (LDPE) Biodegradation by Aspergillus brasiliensis

Daniela Garcia Moreno — 2024-07-26

Low-density polyethylene (LDPE) is a widely used polymer due to its chemical resistance, high flexibility, and mechanical properties. However, its low degradation rate, coupled with its low lifespan and widespread accumulation, poses significant environmental and public health concerns. This study presents a biodegradation model for LDPE using a suspension bioreactor, which could serve as a biological treatment alternative before polymer disposal. In our model, an initial culture of Aspergillus brasiliensis metabolized the carbon within the polymer structure and used it as an energy source, leading to LPDE biodegradation and mineralization. The procedure took place in a laboratory-scale bioreactor prototype under aerobic conditions and submerged liquid fermentation. After one month of culture, a biodegradation percentage of 1:890:56 % was reached. The treated materials were analyzed by scanning electron microscopy (SEM) and fourier transform infrared spectroscopy (FTIR). We found evidence of biodegradation, colonization of the material, and biofilm formation. This research provides preliminary data on the biodegradation of LDPE under submerged liquid fermentation, marking an initial phase in the development of a prototype for polymer biodegradation.